The method and compositions of the present invention are directed to an alternative method of drying drug and nutrient carriers that produce solid, rigid, but rapidly dissolvable drug and nutrient carriers capable of rapid liberation of the active component to the body in a method that yields new and unexpected result over extant methods of freeze drying.
In accordance with an important feature of the present invention, a composition of (1) a hydrogel or foamed, non-toxic, edible solid carrier material, such as a proteinaceous material, particularly gelatin or a gelatin derivative, e.g., gelatin; gelatin A; gelatin B, modified fluid gelatin, albumin, and the like; or hydrogels formed from materials such as acacia, tragatanth, and/or guar gum; or aqueous foams formed with any anionic, cationic or amphoteric surfactant, either synthetic or natural (biosurfactants) e.g., lecithin, or a lipoprotein, e.g. a phospholipid; together with (2) a non-toxic, edible, polysaccharide, capable of rigidifying the hydrogel or foam substance during dehydration thereof, for example, dextran or a dextran derivative, such as maltodextran, can be dried in accordance with the present invention to leave a porous skeleton carrier, preferably of a proteinaceous material, capable of absorbing and/or adsorbing many times its weight in a drug and/or nutrient and the like.
In accordance with one important embodiment of the present invention, the solid, porous, skeletal carrier is formed by drying the fully hydrated gel or foam material from the gel or foamed state by transfer of water from the hydrated material to an alcohol solution, when both the hydrated gel or foam material and the alcohol are frozen or near freezing, without necessitating vacuum conditions, as needed for lyophilization.
A literature search of Chemical Abstracts 1975 to 1988 failed to reveal any reference which anticipates or suggests the water removal methods of this invention or the products produced by such methods.
Reference texts such as Remington's Pharmaceutical Sciences, 15th Edition, 1976, and Lachman et al, The Theory And Practice Of Industrial Pharmacy, Lea & Febiger, 1978, describe the process of lyophilization as a method to stabilize water and heat-sensitive drugs.
Patent references which include lyophilization in their respective methods are exemplified by Alexander U.S. Pat. No. 4,573,883; Lafon U.S. Pat. No. 4,616,047; Vendel U.S. Pat. No. 3,496,267 and Saferstein, et al U.S. Pat. No. 4,752,466. In each of these patents a method involving lyophilizing or freeze drying under vacuum conditions of unstable compositions is disclosed.
Aside from the common use of low temperature, the low temperature drying method of the present invention has very little similarity to the process of lyophilization. The differences of method and product between this invention and the well known lyophilization process will become more apparent hereinafter.
Lyophilization involves the use of mechanical equipment and control of vapor pressure to produce stabilized drugs. In contrast, the method of the present invention includes the use of an organic solvent and is based on the chemical processes of solubilization and dissolution to produce drug and nutrient delivery compositions, preferably under ambient pressure conditions.